Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$104.79	4.263%	$109.2572	$109.26	$109.25	$109.30
Purchase #2	$90.70	13.482%	$102.9282	$102.93	$102.95	$102.90
Purchase #3	$113.63	8.791%	$123.6192	$123.62	$123.60	$123.60
Purchase #4	$67.61	5.474%	$71.311	$71.31	$71.30	$71.30
Purchase #5	$33.56	6.656%	$35.7938	$35.79	$35.80	$35.80
Purchase #6	$160.49	6.800%	$171.4033	$171.40	$171.40	$171.40
Purchase #7	$135.50	7.540%	$145.7167	$145.72	$145.70	$145.70
7 purchase totals =	$706.28		$760.0294	$760.03	$760.00	$760.00